System and method for coding information on a biosensor test strip

ABSTRACT

The present invention provides a test strip for measuring a concentration of an analyte of interest in a biological fluid, wherein the test strip may be encoded with information that can be read by a test meter into which the test strip is inserted.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/285,197 filed Oct. 31, 2011, which is a divisional of U.S. patentapplication Ser. No. 10/871,599, filed Jun. 18, 2004. This applicationclaims the benefit of U.S. Provisional Application No. 60/480,199, filedJun. 20, 2003, the contents of which are hereby incorporated byreference herein.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus for use in measuringconcentrations of an analyte in a biological fluid. The inventionrelates more particularly to a system and method for coding informationon a biosensor test strip.

BACKGROUND OF THE INVENTION

Measuring the concentration of substances in biological fluids is animportant tool for the diagnosis and treatment of many medicalconditions. For example, the measurement of glucose in body fluids, suchas blood, is crucial to the effective treatment of diabetes.

Diabetic therapy typically involves two types of insulin treatment:basal, and meal-time. Basal insulin refers to continuous, e.g.time-released insulin, often taken before bed. Meal-time insulintreatment provides additional doses of faster acting insulin to regulatefluctuations in blood glucose caused by a variety of factors, includingthe metabolization of sugars and carbohydrates. Proper regulation ofblood glucose fluctuations requires accurate measurement of theconcentration of glucose in the blood. Failure to do so can produceextreme complications, including blindness and loss of circulation inthe extremities, which can ultimately deprive the diabetic of use of hisor her fingers, hands, feet, etc.

Multiple methods are known for determining the concentration of analytesin a blood sample, such as, for example, glucose. Such methods typicallyfall into one of two categories: optical methods and electrochemicalmethods. Optical methods generally involve spectroscopy to observe thespectrum shift in the fluid caused by concentration of the analyte,typically in conjunction with a reagent that produces a known color whencombined with the analyte. Electrochemical methods generally rely uponthe correlation between a current (Amperometry), a potential(Potentiometry) or accumulated charge (Coulometry) and the concentrationof the analyte, typically in conjunction with a reagent that producescharge-carriers when combined with the analyte. See, for example, U.S.Pat. Nos. 4,233,029 to Columbus, 4,225,410 to Pace, 4,323,536 toColumbus, 4,008,448 to Muggli, 4,654,197 to Lilja et al., 5,108,564 toSzuminsky et al., 5,120,420 to Nankai et al., 5,128,015 to Szuminsky etal., 5,243,516 to White, 5,437,999 to Diebold et al., 5,288,636 toPollmann et al., 5,628,890 to Carter et al., 5,682,884 to Hill et al.,5,727,548 to Hill et al., 5,997,817 to Crismore et al., 6,004,441 toFujiwara et al., 4,919,770 to Priedel, et al., and 6,054,039 to Shieh,which are hereby incorporated in their entireties. The biosensor forconducting the tests is typically a disposable test strip having areagent thereon that chemically reacts with the analyte of interest inthe biological fluid. The test strip is mated to a nondisposable testmeter such that the test meter can measure the reaction between theanalyte and the reagent in order to determine and display theconcentration of the analyte to the user.

It is common practice in such test meter/test strip systems to ensureproper identification of the test strip in order to ensure proper testresults. For example, a single test meter may be able to analyze severaldifferent types of test strips, wherein each type of test strip isdesigned to test for the presence of a different analyte in thebiological fluid. In order to properly conduct the test, the test metermust know which type of test is to be performed for the test stripcurrently in use.

Also, lot-to-lot variations in the test strips normally requirecalibration information to be loaded into the test meter in order toensure accurate test results. A common practice for downloading suchcalibration information into the test meter is the use of an electronicread-only memory key (ROM key) that is inserted into a socket of thetest meter. Because this calibration data may only be accurate for aparticular production lot of test strips, the user is usually asked toconfirm that the lot number of the test strip currently in use matchesthe lot number for which the ROM key was programmed.

Many other instances in which it is desirable to have informationrelating to the test strip are known to those having skill in the art.Prior art attempts to code information onto the test strip for readingby the test meter have suffered from many problems, including a severelylimited amount of information that can be coded and the use ofrelatively large amounts of test strip surface area for the informationcoding function.

Thus, a system and method are needed that will allow information to becoded onto a biosensor for reading of the information by the test meter.The present invention is directed toward meeting this need.

SUMMARY OF THE INVENTION

The present invention provides a test strip for measuring aconcentration of an analyte of interest in a biological fluid, whereinthe test strip may be encoded with information that can be read by atest meter into which the test strip is inserted.

In one form of the invention, a method for forming a test strip formeasuring a concentration of an analyte of interest in a biologicalfluid is disclosed, the method comprising the steps of: providing abasic test strip design comprising: a substrate having a surface and atleast one measurement electrode formed thereon; a plurality ofconductive contact pads formed upon the substrate surface, including atleast one information contact pad and at least one measurement contactpad; and a plurality of potential conductive links conductively couplingvarious ones of the plurality of contact pads; wherein the at least oneinformation contact pad is not coupled to any of the at least onemeasurement electrodes except by one or more of the plurality ofpotential conductive links, and the at least one measurement contact padis coupled to one of the at least one measurement electrodes by a pathother than one or more of the plurality of potential conductive links;defining a set of valid test strip designs; wherein each one of the setof valid test strip designs incorporates none, one or more than one ofthe plurality of potential conductive links; and wherein at least one ofthe plurality of potential conductive links couples a first one of theinformation contact pads to a first one of the measurement contact padsin a first valid test strip design, and at least one of the plurality ofpotential conductive links couples the first one of the informationcontact pads to a second one of the measurement contact pads in a secondvalid test strip design; selecting one design from the set of valid teststrip designs; and forming a test strip per said selected one design.

In another form of the invention, a plurality of test strips formeasuring a concentration of an analyte of interest in a biologicalfluid is disclosed, each of the plurality of test strips beingsubstantially identical to one another except for a presence or absenceof a plurality of potential conductive links, at least one of the teststrips comprising: a substrate having a surface and at least onemeasurement electrode formed thereon; a plurality of conductive contactpads formed upon the substrate surface, including at least oneinformation contact pad and at least one measurement contact pad; and aplurality of conductive links selected from the plurality of potentialconductive links, wherein the plurality of conductive links conductivelycouple at least three contact pads together; wherein the at least oneinformation contact pad is not coupled to any of the at least onemeasurement electrodes except by one or more of the plurality ofpotential conductive links, and the at least one measurement contact padis coupled to one of the at least one measurement electrodes by a pathother than one or more of the plurality of potential conductive links.

In another form of the invention, a method for forming a test strip formeasuring a concentration of an analyte of interest in a biologicalfluid is disclosed, the method comprising the steps of: providing abasic test strip design comprising: a substrate having a surface and atleast one measurement electrode formed thereon; a plurality ofconductive contact pads formed upon the substrate surface, including atleast one information contact pad and at least one measurement contactpad; and a plurality of potential conductive links conductively couplingvarious ones of the plurality of contact pads; wherein the at least oneinformation contact pad is not coupled to any of the at least onemeasurement electrodes except by one or more of the plurality ofpotential conductive links, and the at least one measurement contact padis coupled to one of the at least one measurement electrodes by a pathother than one or more of the plurality of potential conductive links;defining a set of valid test strip designs; wherein each one of the setof valid test strip designs incorporates none, one or more than one ofthe plurality of potential conductive links; and wherein at least one ofthe set of valid test strip designs includes conductive links thatconductively couple at least three contact pads together; selecting onedesign from the set of valid test strip designs; and forming a teststrip per said selected one design.

In another form of the invention, a test strip for measuring aconcentration of an analyte of interest in a biological fluid isdisclosed, the test strip comprising: a substrate having a surface andat least one measurement electrode formed thereon; a plurality ofconductive contact pads formed upon the substrate surface, including atleast one information contact pad and at least one measurement contactpad; and at least one conductive link conductively coupling at leastthree of the contact pads; wherein the at least one information contactpad is not coupled to any of the at least one measurement electrodesexcept by one or more of the at least one conductive links, and the atleast one measurement contact pad is coupled to one of the at least onemeasurement electrodes by a path other than one or more of the at leastone conductive links.

In another form of the invention, a test strip for measuring aconcentration of an analyte of interest in a biological fluid isdisclosed, the test strip comprising: a substrate having a surface andat least one measurement electrode formed thereon; a plurality ofconductive contact pads formed upon the substrate surface, including atleast one information contact pad and at least one measurement contactpad; and at least one conductive link conductively coupling at leastthree of the contact pads; wherein the at least one information contactpad is not coupled to any of the at least one measurement electrodesexcept by one or more of the at least one conductive links, and the atleast one measurement contact pad is coupled to one of the at least onemeasurement electrodes by a path other than one or more of the at leastone conductive links.

In another form of the invention, a test strip for measuring aconcentration of an analyte of interest in a biological fluid isdisclosed, the test strip adapted to be inserted into a test meterhaving at least one connector contact that touches the inserted teststrip, the test strip comprising: a substrate having a top surface; aconductive layer formed on at least a portion of the substrate topsurface; and at least one predetermined contact pad position definedupon the substrate top surface; wherein each of the at least one contactpad positions is touched by a respective one of the at least oneconnector contacts when the at least one connector contacts touch thetest strip; wherein a presence of the conductive layer in a respectiveone of the contact pad positions is operative to indicate a first stateof a binary bit to the test meter; and wherein an absence of theconductive layer in a respective one of the contact pad positions isoperative to indicate a second state of a binary bit to the test meter.

In another form of the invention, a method for measuring a concentrationof an analyte of interest in a biological fluid, comprising the stepsof: providing a test meter having at least one connector contact thattouches an inserted test strip, providing a test strip adapted to beinserted into the test meter, the test strip comprising: a substratehaving a top surface; a conductive layer formed on at least a portion ofthe substrate top surface; and at least one predetermined contact padposition defined upon the substrate top surface; touching each of the atleast one predetermined contact pad positions with a respective one ofthe at least one connector contacts; indicating a first state of abinary bit within the test meter in response to a presence of theconductive layer in a respective one of the contact pad positions; andindicating a second state of a binary bit within the test meter inresponse to an absence of the conductive layer in a respective one ofthe contact pad positions.

In another form of the invention, a test strip for measuring aconcentration of an analyte of interest in a biological fluid isdisclosed, the test strip comprising a substrate having a surface; afirst measurement electrode formed on the surface; a second measurementelectrode formed on the surface; a third potential electrode formed onthe surface; a fourth potential electrode formed on the surface; a firstcontact pad formed on the surface and conductively coupled to the firstmeasurement electrode; a second contact pad formed on the surface andconductively coupled to the second measurement electrode; a thirdcontact pad formed on the surface and conductively coupled to the thirdpotential electrode; a fourth contact pad formed on the surface andconductively coupled to the fourth potential electrode; and a conductivelink coupling one of the third and fourth potential electrodes to thefirst measurement electrode, whereby another one of the third and fourthpotential electrodes becomes an actual electrode.

In another form of the invention, a method of using a test meter andassociated test strip for measuring a concentration of an analyte ofinterest in a biological fluid is disclosed, comprising the steps of a)providing a test strip comprising a substrate having at least a first,second and third contact pad formed thereon; b) providing a test metercomprising a connector configured to make conductive contact with thefirst, second and third contact pads when the test strip is insertedinto the test meter; c) operating the test meter to determine ifconductivity exists between the first and second contact pads; d)operating the test meter to determine if conductivity exists between thefirst and third contact pads; e) designating the second contact pad tohave a first function and the third contact pad to have a secondfunction if the test meter determines that conductivity exists betweenthe first and second contact pads and that conductivity does not existbetween the first and third contact pads; and f) designating the secondcontact pad to have the second function and the third contact pad tohave the first function if the test meter determines that conductivitydoes not exist between the first and second contact pads and thatconductivity exists between the first and third contact pads.

In another form of the invention, a method of using a test meter andassociated test strip for measuring a concentration of an analyte ofinterest in a biological fluid is disclosed, comprising the steps of a)providing a test strip comprising a substrate having at least a first,second and third contact pad formed thereon; b) providing a test metercomprising a connector configured to make conductive contact with thefirst, second and third contact pads when the test strip is insertedinto the test meter; c) operating the test meter to determine ifconductivity exists between the first and second contact pads; d)designating the second contact pad to have a first function and thethird contact pad to have a second function if the test meter determinesthat conductivity exists between the first and second contact pads; ande) designating the second contact pad to have the second function andthe third contact pad to have the first function if the test meterdetermines that conductivity does not exist between the first and secondcontact pads.

In another form of the invention, a method of using a test meter adaptedto measure a concentration of an analyte of interest in a biologicalfluid placed on a test strip is disclosed, the method comprising thesteps of a) inserting the test strip into the test meter such that thetest meter makes electrical contact with the test strip; b) operatingthe meter to read information encoded onto the test strip; and c)choosing a language in which the test meter displays user operatinginstructions based upon the information read from the test strip.

In another form of the invention, a method of using a test meter adaptedto measure a concentration of an analyte of interest in a biologicalfluid placed on a test strip is disclosed, the method comprising thesteps of a) inserting the test strip into the test meter such that thetest meter makes electrical contact with the test strip; b) operatingthe meter to read information encoded onto the test strip; and c)determining if the test meter and the test strip were sold in the samegeographic market based upon the information read from the test strip.

In another form of the invention, a method of using a test meter adaptedto measure a concentration of an analyte of interest in a biologicalfluid placed on a test strip is disclosed, wherein the test meter is notintended for use with subscription test strips sold on a subscriptionbasis, the method comprising the steps of a) inserting the test stripinto the test meter such that the test meter makes electrical contactwith the test strip; b) operating the meter to read information encodedonto the test strip; c) determining if the test strip is a subscriptiontest strip based upon the information read from the test strip; and d)preventing use of the test strip by the meter if the test strip is asubscription test strip.

In another form of the invention, a method of using a test meter adaptedto measure a concentration of an analyte of interest in a biologicalfluid placed on a test strip is disclosed, the method comprising thesteps of a) inserting the test strip into the test meter such that thetest meter makes electrical contact with the test strip; b) operatingthe meter to read information encoded onto the test strip; and c)activating a latent feature of the test meter based upon the informationread from the test strip.

In another form of the invention, a method of using a test meter adaptedto measure a concentration of an analyte of interest in a biologicalfluid placed on a test strip is disclosed, the method comprising thesteps of a) inserting the test strip into the test meter such that thetest meter makes electrical contact with the test strip; b) operatingthe meter to read information encoded onto the test strip; and c)changing the user operating instructions displayed to the user basedupon the information read from the test strip.

In another form of the invention, a test system for measuring aconcentration of an analyte of interest in a biological fluid isdisclosed, the test system comprising a test meter comprising aconnector having at least ten contacts; and a test strip adapted to beinserted into the test meter connector, the test strip comprising: asubstrate having a surface; at least ten contact pads formed on thesurface; wherein the at least ten contacts make contact with therespective at least ten contact pads when the test strip is insertedinto the test meter connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a first typical test strip foruse in measuring the concentration of an analyte of interest in abiological fluid.

FIG. 2 is a schematic plan view of a first embodiment test stripelectrode and contact pad arrangement according to the presentinvention.

FIG. 3 is a table showing a first embodiment coding sequence for thetest strip of FIG. 2.

FIG. 4 is a perspective view of a second typical test strip for use inmeasuring the concentration of an analyte of interest in a biologicalfluid.

FIG. 5 illustrates a view of an ablation apparatus suitable for use withthe present invention.

FIG. 6 is a view of the laser ablation apparatus of FIG. 5 showing asecond mask.

FIG. 7 is a view of an ablation apparatus suitable for use with thepresent invention.

FIG. 8 is a schematic process flow diagram of a prior art process forverifying the applicability of the calibration data in the test meter tothe test strip currently inserted into the test meter.

FIG. 9 is a schematic process flow diagram of a first embodiment processof the present invention for verifying the applicability of thecalibration data in the test meter to the test strip currently insertedinto the test meter.

FIG. 10 is a schematic plan view of a second embodiment test stripelectrode and contact pad arrangement according to the presentinvention.

FIG. 11 is a schematic plan view of a third embodiment test stripelectrode and contact pad arrangement according to the presentinvention.

FIG. 12 is a schematic plan view of an electrical connector-to-teststrip contact pad interface illustrating worst case left tolerancestack-ups.

FIG. 13 is a schematic plan view of the electrical connector-to-teststrip contact pad interface of FIG. 12 illustrating normal casetolerance stack-ups.

FIG. 14 is a schematic plan view of the electrical connector-to-teststrip contact pad interface of FIG. 12 illustrating worst case righttolerance stack-ups.

FIG. 15 is a schematic plan view of a fourth embodiment test stripelectrode and contact pad arrangement according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings, and specific language will be used to describe thatembodiment. It will nevertheless be understood that no limitation of thescope of the invention is intended. Alterations and modifications in theillustrated device, and further applications of the principles of theinvention as illustrated therein, as would normally occur to one skilledin the art to which the invention relates are contemplated, are desiredto be protected. In particular, although the invention is discussed interms of a blood glucose meter, it is contemplated that the inventioncan be used with devices for measuring other analytes and other sampletypes. Such alternative embodiments require certain adaptations to theembodiments discussed herein that would be obvious to those skilled inthe art.

Although the system and method of the present invention may be used withtest strips having a wide variety of designs and made with a widevariety of construction techniques and processes, a typicalelectrochemical test strip is illustrated in FIG. 1, and indicatedgenerally at 10. Referring to FIG. 1, the test strip 10 comprises abottom substrate 12 formed from an opaque piece of 350 μm thickpolyester (such as Melinex 329 available from DuPont) coated on its topsurface with a 50 nm conductive (gold) layer (by sputtering or vapordeposition, for example). Electrodes, connecting traces and contact padstherefor are then patterned in the conductive layer by a laser ablationprocess. The laser ablation process is performed by means of an excimerlaser which passes through a chrome-on-quartz mask. The mask patterncauses parts of the laser field to be reflected while allowing otherparts of the field to pass through, creating a pattern on the gold whichis ablated where contacted by the laser light. The laser ablationprocess is described in greater detail hereinbelow. For example, working20, counter 22, dose sufficiency working 24, and dose sufficiencycounter 26 electrodes may be formed as shown and coupled, respectively,to measurement contact pads W, C, DW and DC. These contact pads providea conductive area upon the test strip 10 to be contacted by a connectorcontact of the test meter once the test strip 10 is inserted into thetest meter.

The bottom substrate 12 is then coated in the area extending over theelectrodes with a reagent layer 14 as a continuous, extremely thinreagent film. The reagent layer 14 is a stripe of approximately 6millimeters width across the substrate 12 in the region labeled “ReagentLayer” on FIG. 1. For example, this region may be coated at a wet-coatweight of 50 grams per square meter of coated surface area. The reagentstrip is dried conventionally with an in-line drying system where thenominal air temperature is at 110° C. The rate of processing isnominally 30-38 meters per minute and depends upon the rheology of thereagent.

The materials are processed in continuous reels such that the electrodepattern is orthogonal to the length of the reel, in the case of thesubstrate 12. Once the substrate 12 has been coated with reagent, thespacers 16 are slit and placed in a reel-to-reel process onto thesubstrate 12. Two spacers 16 formed from 100 μm polyester (for example,Melinex 329 available from DuPont) coated with 25 μm PSA (hydrophobicadhesive) on both the dorsal and ventral surfaces are applied to thebottom substrate 12, such that the spacers 16 are separated by 1.5 mmand the working, counter and dose sufficiency electrodes are centered inthis gap. A top foil layer 18 formed from 100 μm polyester coated with ahydrophilic film on its ventral surface (using the process described inU.S. Pat. No. 5,997,817) is placed over the spacers 16. The hydrophilicfilm is coated with a mixture of Vitel and Rhodapex surfactant at anominal thickness of 10 microns. The top foil layer 18 is laminatedusing a reel-to-reel process. The test strips can then be produced fromthe resulting reels of material by means of slitting and cutting.

Although the basic test strip 10 illustrated in FIG. 1 can provideaccurate measurements of blood glucose in a whole blood sample, it doesnot provide any means for the test meter into which it is inserted toidentify anything about the test strip. The present invention presentsseveral systems by which information relating to the test strip can becoded directly onto the test strip itself, such that this informationcan be conveyed to a test meter into which the test strip is inserted.

In a first embodiment of the present invention, information about thetest strip can be coded directly onto the test strip by the addition oftwo or more contact pads dedicated to reading such coded information. Asillustrated in FIG. 2, a pair of additional information contact pads B1and B2 are added to the proximal end of the test strip. Additionally,potential conductive links between the information contact pads B1 andB2 and between them and measurement contact pads connected to test stripmeasurement electrodes are identified at 28, 30, 32, 34 and 36. Theselinks are denominated as potential conductive links because they mayeither be present or absent in the finished test strip, depending uponthe information that is to be coded onto the test strip. Therefore, a“potential conductive link” indicates a conductive link that is found onsome, but not all, of a group of otherwise substantially identical teststrips. As used herein, the phrase “information contact pad” is definedas a contact pad on the test strip that is either not conductivelycoupled to a measurement electrode of the test strip at all, or is socoupled only by a potential conductive link. As used herein, the phrase“measurement contact pad” is defined as a contact pad on the test stripthat is always conductively coupled to a measurement electrode of thetest strip, regardless of the presence or absence of the potentialconductive links.

Specifically, potential conductive link 28 couples the DC contact padand the B1 contact pad. Potential conductive link 30 couples the B1contact pad and the B2 contact pad. Potential conductive link 32 couplesthe B2 contact pad and the C contact pad. Potential conductive link 34couples the DC contact pad and the B2 contact pad. Potential conductivelink 36 couples the B1 contact pad and the C contact pad. It should benoted that the first embodiment of the present invention illustratespotential conductive links between the information contact pads B1 andB2 and the measurement contact pads DC and C by way of example only, andthat the information contact pads may be conductively linked to anydesired measurement contact pad(s) on the test strip.

FIG. 3 illustrates a table showing the possible combinations for thepotential conductive links 28-36 formed on any one test strip of thefirst embodiment. The first five columns of the table represent each ofthe potential conductive links 28-36, which are labeled C1-C5,respectively. Each of the nine rows of the table numbered 0-8 representa different number that can be encoded using the potential conductivelinks 28-36. A “0” in a table position indicates that the potentialconductive link is not formed when encoding the number of that row,while a “1” in a table position indicates that the potential conductivelink is formed when encoding the number of that row. Note that there aresome combinations of potential conductive links that are not allowedbecause the DC contact pad and the C contact pad cannot be conductivelylinked without harming the measurement functionality of the test stripmeasurement electrodes. For example, potential conductive links 34 and36 may not be used at the same time, as they cross one another andtherefore would conductively connect the DC contact pad to the C contactpad. Similarly, potential conductive links 28, 30 and 32 may not be usedat the same time.

The last two columns of the table of FIG. 3 are labeled B1 and B2,respectively, and indicate to which of the other contact pads thelabeled contact pad is coupled when the number of that row is encodedonto the test strip. For example, when the number six (6) is encodedonto the test strip (i.e. potential conductive links 28 and 32 areformed on the test strip) the B1 contact pad is conductively coupled tothe DC contact pad, and the B2 contact pad is conductively coupled tothe C contact pad, but B1 and B2 are not conductively coupled to anyother contact pads (including to each other). Therefore, a measurementby the test meter of the resistance (either directly or indirectly)between each of the contact pads DC, B1, B2 and C will indicate which ofthe eight (8) possible numbers has been encoded onto the test strip. Thepresent invention also comprehend other methods for determining thepresence or absence of potential conductive links on the test stripother than by measurement of resistance or conductivity. By way ofnon-limiting example, the potential conductive links can also be sensedin a non-contact fashion by inducing and sensing eddy currents using anelectromagnetic field, by capacitive means, by optical scanningtechniques, or by other methods that would be apparent to one havingordinary skill in the art.

Note that the absence of all of the potential conductive links 28-36 ispreferably not considered to be a valid state as this could be caused bya localized defect obliterating the region of the test strip containingthe potential conductive links 28-36, but this state could be considereda valid state in other, non-preferred, embodiments. It should also benoted that a reading of conduction between combinations of contact padsnot indicated as a valid combination in the table of FIG. 3 will beinterpreted by the test meter as a defective strip with an unintendedshort.

It will be appreciated that the use of measurement contact pads incombination with dedicated information contact pads in the presentinvention, and the opportunity to potentially couple each informationcontact pad to more than one measurement contact pad significantlyincreases the amount of numbers that may be encoded onto the test strip.By way of comparison, the two (2) information contact pads of the firstembodiment of the present invention conservatively allow the coding ofeight (8) numbers. The design disclosed in JP 2000352034 would onlyallow two (2) possible states with two information contact pads, whilethe design disclosed in EP 1152239A1 would only allow four (4) possiblestates with two information contact pads.

One method of preparing a test strip encoded with information asdescribed herein is by the use of laser ablation techniques. Examples ofthe use of these techniques in preparing electrodes for biosensors aredescribed in U.S. patent application Ser. No. 09/866,030, “Biosensorswith Laser Ablation Electrodes with a Continuous Coverlay Channel” filedMay 25, 2001, and in U.S. patent application Ser. No. 09/411,940,entitled “Laser Defined Features for Patterned Laminates and Electrode,”filed Oct. 4, 1999, both disclosures incorporated herein by reference.

It is desirable in the present invention to provide for the accurateplacement of the electrical components relative to one another and tothe overall biosensor. In a preferred embodiment, the relative placementof components is achieved, at least in part, by the use of broad fieldlaser ablation that is performed through a mask or other device that hasa precise pattern for the electrical components. This allows accuratepositioning of adjacent edges, which is further enhanced by the closetolerances for the smoothness of the edges.

FIG. 4 illustrates a simple biosensor 401 useful for illustrating thelaser ablation process of the present invention, including a substrate402 having formed thereon conductive material 403 defining electrodesystems comprising a first electrode set 404 and a second electrode set405, and corresponding traces 406, 407 and contact pads 408, 409,respectively. The conductive material 403 may contain pure metals oralloys, or other materials, which are metallic conductors. Preferably,the conductive material is absorptive at the wavelength of the laserused to form the electrodes and of a thickness amenable to rapid andprecise processing. Non-limiting examples include aluminum, carbon,copper, chromium, gold, indium tin oxide (ITO), palladium, platinum,silver, tin oxide/gold, titanium, mixtures thereof, and alloys ormetallic compounds of these elements. Preferably, the conductivematerial includes noble metals or alloys or their oxides. Mostpreferably, the conductive material includes gold, palladium, aluminum,titanium, platinum, ITO and chromium. The conductive material ranges inthickness from about 10 nm to 80 nm, more preferably, 30 nm to 70 nm,and most preferably 50 nm. It is appreciated that the thickness of theconductive material depends upon the transmissive property of thematerial and other factors relating to use of the biosensor.

While not illustrated, it is appreciated that the resulting patternedconductive material can be coated or plated with additional metallayers. For example, the conductive material may be copper, which isthen ablated with a laser into an electrode pattern; subsequently, thecopper may be plated with a titanium/tungsten layer, and then a goldlayer, to form the desired electrodes. Preferably, a single layer ofconductive material is used, which lies on the base 402. Although notgenerally necessary, it is possible to enhance adhesion of theconductive material to the base, as is well known in the art, by usingseed or ancillary layers such as chromium nickel or titanium. Inpreferred embodiments, biosensor 401 has a single layer of gold,palladium, platinum or ITO.

Biosensor 401 is illustratively manufactured using two apparatuses 10,10′, shown in FIGS. 4,6 and 7, respectively. It is appreciated thatunless otherwise described, the apparatuses 410, 410′ operate in asimilar manner. Referring first to FIG. 5, biosensor 401 is manufacturedby feeding a roll of ribbon 420 having an 80 nm gold laminate, which isabout 40 mm in width, into a custom fit broad field laser ablationapparatus 410. The apparatus 410 comprises a laser source 411 producinga beam of laser light 412, a chromium-plated quartz mask 414, and optics416. It is appreciated that while the illustrated optics 416 is a singlelens, optics 416 is preferably a variety of lenses that cooperate tomake the light 412 in a pre-determined shape.

A non-limiting example of a suitable ablation apparatus 410 (FIGS. 5-6)is a customized MicrolineLaser 200-4 laser system commercially availablefrom LPKF Laser Electronic GmbH, of Garbsen, Germany, which incorporatesan LPX-400, LPX-300 or LPX-200 laser system commercially available fromLambda Physik AG, Göttingen, Germany and a chromium-plated quartz maskcommercially available from International Phototool Company, ColoradoSprings, Co.

For the MicrolineLaser 200-4 laser system (FIGS. 5-6), the laser source411 is a LPX-200 KrF-UV-laser. It is appreciated, however, that higherwavelength UV lasers can be used in accordance with this disclosure. Thelaser source 411 works at 248 nm, with a pulse energy of 600 mJ, and apulse repeat frequency of 50 Hz. The intensity of the laser beam 412 canbe infinitely adjusted between 3% and 92% by a dielectric beamattenuator (not shown). The beam profile is 27×15 mm² (0.62 sq. inch)and the pulse duration 25 ns. The layout on the mask 414 ishomogeneously projected by an optical elements beam expander,homogenizer, and field lens (not shown). The performance of thehomogenizer has been determined by measuring the energy profile. Theimaging optics 416 transfer the structures of the mask 414 onto theribbon 420. The imaging ratio is 2:1 to allow a large area to be removedon the one hand, but to keep the energy density below the ablation pointof the applied chromium mask on the other hand. While an imaging of 2:1is illustrated, it is appreciated that the any number of alternativeratios are possible in accordance with this disclosure depending uponthe desired design requirements. The ribbon 420 moves as shown by arrow425 to allow a number of layout segments to be ablated in succession.

The positioning of the mask 414, movement of the ribbon 420, and laserenergy are computer controlled. As shown in FIG. 5, the laser beam 412is projected onto the ribbon 420 to be ablated. Light 412 passingthrough the clear areas or windows 418 of the mask 414 ablates the metalfrom the ribbon 420. Chromium coated areas 424 of the mask 414 blocksthe laser light 412 and prevent ablation in those areas, resulting in ametallized structure on the ribbon 420 surface. Referring now to FIG. 6,a complete structure of electrical components may require additionalablation steps through a second mask 414′. It is appreciated thatdepending upon the optics and the size of the electrical component to beablated, that only a single ablation step or greater than two ablationsteps may be necessary in accordance with this disclosure. Further, itis appreciated that instead of multiple masks, that multiple fields maybe formed on the same mask in accordance with this disclosure.

Specifically, a second non-limiting example of a suitable ablationapparatus 410′ (FIG. 7) is a customized laser system commerciallyavailable from LPKF Laser Electronic GmbH, of Garbsen, Germany, whichincorporates a Lambda STEEL (Stable energy excimer laser) laser systemcommercially available from Lambda Physik AG, Göttingen, Germany and achromium-plated quartz mask commercially available from InternationalPhototool Company, Colorado Springs, Co. The laser system features up to1000 mJ pulse energy at a wavelength of 308 nm. Further, the lasersystem has a frequency of 100 Hz. The apparatus 410′ may be formed toproduce biosensors with two passes as shown in FIGS. 5 and 6, butpreferably its optics permit the formation of a 10×40 mm pattern in a 25ns single pass.

While not wishing to be bound to a specific theory, it is believed thatthe laser pulse or beam 412 that passes through the mask 414, 414′, 414″is absorbed within less than 1 μm of the surface 402 on the ribbon 420.The photons of the beam 412 have an energy sufficient to causephoto-dissociation and the rapid breaking of chemical bonds at themetal/polymer interface. It is believed that this rapid chemical bondbreaking causes a sudden pressure increase within the absorption regionand forces material (metal film 403) to be ejected from the polymer basesurface. Since typical pulse durations are around 20-25 nanoseconds, theinteraction with the material occurs very rapidly and thermal damage toedges of the conductive material 403 and surrounding structures isminimized. The resulting edges of the electrical components have highedge quality and accurate placement as contemplated by the presentinvention.

Fluence energies used to remove or ablate metals from the ribbon 420 aredependent upon the material from which the ribbon 420 is formed,adhesion of the metal film to the base material, the thickness of themetal film, and possibly the process used to place the film on the basematerial, i.e. supporting and vapor deposition. Fluence levels for goldon KALADEX® range from about 50 to about 90 mJ/cm², on polyimide about100 to about 120 mJ/cm², and on MELINEX® about 60 to about 120 mJ/cm².It is understood that fluence levels less than or greater than the abovementioned can be appropriate for other base materials in accordance withthe disclosure.

Patterning of areas of the ribbon 420 is achieved by using the masks414, 414′. Each mask 414, 414′ illustratively includes a mask field 422containing a precise two-dimensional illustration of a pre-determinedportion of the electrode component patterns to be formed. FIG. 5illustrates the mask field 422 including contact pads and a portion oftraces. As shown in FIG. 6, the second mask 414′ contains a secondcorresponding portion of the traces and the electrode patternscontaining fingers. As previously described, it is appreciated thatdepending upon the size of the area to be ablated, the mask 414 cancontain a complete illustration of the electrode patterns (FIG. 7), orportions of patterns different from those illustrated in FIGS. 5 and 6in accordance with this disclosure. Preferably, it is contemplated thatin one aspect of the present invention, the entire pattern of theelectrical components on the test strip are laser ablated at one time,i.e., the broad field encompasses the entire size of the test strip(FIG. 7). In the alternative, and as illustrated in FIGS. 5 and 6,portions of the entire biosensor are done successively.

While mask 414 will be discussed hereafter, it is appreciated thatunless indicated otherwise, the discussion will apply to masks 414′,414″ as well. Referring to FIG. 5, areas 424 of the mask field 422protected by the chrome will block the projection of the laser beam 412to the ribbon 420. Clear areas or windows 418 in the mask field 422allow the laser beam 412 to pass through the mask 414 and to impactpredetermined areas of the ribbon 420. As shown in FIG. 5, the cleararea 418 of the mask field 422 corresponds to the areas of the ribbon420 from which the conductive material 403 is to be removed.

Further, the mask field 422 has a length shown by line 430 and a widthas shown by line 432. Given the imaging ratio of 2:1 of the LPX-200, itis appreciated that the length 30 of the mask is two times the length ofa length 434 of the resulting pattern and the width 432 of the mask istwo times the width of a width 436 of the resulting pattern on ribbon420. The optics 416 reduces the size of laser beam 412 that strikes theribbon 420. It is appreciated that the relative dimensions of the maskfield 422 and the resulting pattern can vary in accordance with thisdisclosure. Mask 414′ (FIG. 6) is used to complete the two-dimensionalillustration of the electrical components.

Continuing to refer to FIG. 5, in the laser ablation apparatus 410 theexcimer laser source 411 emits beam 412, which passes through thechrome-on-quartz mask 414. The mask field 422 causes parts of the laserbeam 412 to be reflected while allowing other parts of the beam to passthrough, creating a pattern on the gold film where impacted by the laserbeam 412. It is appreciated that ribbon 420 can be stationary relativeto apparatus 410 or move continuously on a roll through apparatus 410.Accordingly, non-limiting rates of movement of the ribbon 420 can befrom about 0 m/min to about 100 m/min, more preferably about 30 m/min toabout 60 m/min. It is appreciated that the rate of movement of theribbon 420 is limited only by the apparatus 410 selected and may wellexceed 100 m/min depending upon the pulse duration of the laser source411 in accordance with the present disclosure.

Once the pattern of the mask 414 is created on the ribbon 420, theribbon is rewound and fed through the apparatus 410 again, with mask414′ (FIG. 6). It is appreciated, that alternatively, laser apparatus410 could be positioned in series in accordance with this disclosure.Thus, by using masks 414, 414′, large areas of the ribbon 420 can bepatterned using step-and-repeat processes involving multiple mask fields422 in the same mask area to enable the economical creation of intricateelectrode patterns and other electrical components on a substrate of thebase, the precise edges of the electrode components, and the removal ofgreater amounts of the metallic film from the base material.

The ability to code information directly onto the test strip candramatically increase the capabilities of the test strip and enhance itsinteraction with the test meter. For example, it is well known in theart to supply the test meter with calibration data applicable to anygiven manufacturing lot of test strips. Typically, this is done bysupplying a read-only memory key (ROM key) with each vial of teststrips, where the ROM key has encoded thereon the calibration dataapplicable to the test strips in the vial. Before using the test stripsfrom the vial, the user inserts the ROM key into a port in the testmeter so that the test meter may have access to this data whileperforming tests using the test strip. The quality of the measurementresult can be verified by allowing the meter to electronically assessthe applicability of the ROM key data to the test strip currentlyinserted into the meter, without the need for an optical reader to readbar code information on the test strip as has been taught in the priorart.

Current commercially-available products require the user to be involvedin verifying the correct ROM key has been inserted into the test meterfor the test strip currently being used. For example, FIG. 8 illustratesa typical prior art process for verifying the match between the ROM keydata and the test strip lot identification (ID) number. Prior toexecuting this process, the ROM key has been inserted into the testmeter, the ROM data has been loaded into the test meter, and the testmeter is turned off. The process begins by inserting a test strip (step100) into the test meter, which causes the test meter to automaticallyturn on (step 102). The test meter displays the lot ID of the currentlyloaded calibration data (step 104) in order to give the user the chanceto verify that this lot ID matches the lot ID printed on thevial/package (for example) containing a plurality of test strips fromthe same production lot as the test strip currently inserted into thetest meter.

Because the process relies upon the user to perform this check, there isno way to guarantee that it is done or if it is, that it is doneaccurately. The process of FIG. 8 therefore indicates an optional stepfor the user to compare the lot ID on the test meter display to the lotID on the test strip vial (step 106) and to determine (step 108) ifthere is a match. If the two lot IDs do not match, then the user shouldremove the test strip (step 110) and insert the ROM key that matches thetest strip vial into the test meter (step 112) so that the propercalibration code can be loaded into the test meter. The process wouldthen start over at step 100 with the insertion of the test strip. Onceit has been determined that the test meter's calibration code lot IDmatches the lot ID of the test strip (step 108), then the measurementsequence can continue by applying blood to the test strip (step 114) andbeginning the blood glucose measurement cycle (step 116).

It will be appreciated that responsibility for verification of theaccuracy of the measurement calibration data has been placed completelyin the hands of the user in the prior art process of FIG. 8. It issometimes encountered that users ignore stated use instructions providedwith the test strips. One such example is the removal of test stripsfrom a first vial that were manufactured in lot X and consolidatingthese test strips into a second vial containing test strips manufacturedin lot Y. Therefore, it is desirable to bring lot specific calibrationinformation to the individual test strip level instead of to the viallevel as is done in the prior art.

In order to remove the possibility of human error or neglect from theprocess, and to thereby improve the quality of the measurement, theinformation contact pads of the present invention allow the test meteritself to perform checks as to the applicability of the currently loadedcalibration data to the currently inserted test strip. A firstembodiment process of the present invention to allow the test meter toactively participate in such verification is illustrated in FIG. 9. Thesteps of the process of FIG. 9 that are identical to the correspondingsteps in FIG. 8 are numbered with the same reference designators.

Prior to executing this process, the ROM key has been inserted into thetest meter, the ROM data has been loaded into the test meter, and thetest meter is turned off. The process begins by inserting a test strip(step 100) into the test meter, which causes the test meter toautomatically turn on (step 102). The test meter then measures theconductivity between the various information and measurement contactpads on the test strip that have been designated for encodinginformation onto the test strip in order to ascertain the lot or familyID of the test strip (step 200). Depending upon the quantity ofinformation that may be encoded onto the test strip, it may or may notbe possible to code a unique production lot number onto the test strip.If there is not sufficient space for unique production lot IDs to beencoded, it is still possible to encoded calibration family informationonto the test strip. For example, the test strips usable in the testmeter may be of two or more families where significant differences existbetween the family test strip designs. For example, two families may usea different reagent on the test strip. In such situations, the testmeter can still verify that the loaded calibration data matches the teststrip family encoded onto the test strip, even if it is not possible toverify the precise production lot of the test strip. Therefore, as usedherein, the phrase “lot ID” is intended to encompass any informationthat identifies a group to which the test strip or calibration databelongs, even if that group is not as small as a production lot of thetest strip.

Returning to the process of FIG. 9, the test meter compares (step 202)the lot ID of the calibration data stored within the ROM key currentlyinserted into the meter (or calibration data previously-loaded into thetest meter internal memory) to the lot ID read from the test strip. Ifthey do not match, the test meter displays the lot ID of the currentlyloaded calibration data (step 204) and a warning in order to give theuser the chance to insert a correct test strip or to insert a differentROM key into the test meter. Alternatively, the test meter may simplydisplay an error message to the user. The fact that the lot IDs do notmatch is flagged (step 206) in the test meter's result memory 208 sothat there is a record in the memory 208 that the measurement resultobtained is suspect in view of the discrepancy in the lot IDs.Alternatively, the user may be prohibited from running a test and theprocess may be aborted.

Because in some embodiments it is desired that the test meter not becompletely disabled if the lot IDs do not match, the process of FIG. 9indicates an optional step for the user to compare the lot ID on thetest meter display to the lot ID on the test strip vial (step 106) andto determine (step 108) if there is a match. If the two lot IDs do notmatch, then the user should remove the test strip (step 110) and insertthe ROM key that matches the test strip vial into the test meter (step112) so that the proper calibration code can be loaded into the testmeter. The process would then start over at step 100 with the insertionof the test strip.

Also optionally, if the test meter has the capacity to store more thanone calibration dataset within the meter's internal memory, then themeter may determine the multiple lot IDs of calibration data that may bestored within the test meter and automatically choose the calibrationdataset that matches the test strip currently inserted into the meter.The meter can then return to step 114.

Once it has been determined that the test meter's calibration code lotID matches the lot ID of the test strip (step 108), then the measurementsequence can continue by applying blood to the test strip (step 114) andbeginning the blood glucose measurement cycle (step 116). It will beappreciated that the process of FIG. 9 represents an improvement overthe prior art process of FIG. 8 in that the user is automatically warnedwhen the lot ID of the test strip does not match the lot ID of thecurrently-selected calibration dataset. Furthermore, if a test isconducted with this mismatched combination, then the result memorywithin the test meter is flagged to indicate that the result may not beas accurate as would be the case if the correct calibration dataset wereused.

As a further example of the usefulness of encoding information directlyonto the test strip, the present invention allows the test strip toactivate or deactivate certain features programmed into the test meter.For example, a single test meter may be designed to be used in severaldifferent geographic markets, where a different language is spoken ineach market. By encoding the test strips with information indicating inwhich market the test strips were sold, the encoded information cancause the test meter to display user instructions and data in a languagethat is appropriate for that market. Also, a meter may be designed forsale in a certain geographic market and it is desired that the meter notbe used with test strips obtained in a different geographic market (forexample when governmental regulations require the test strips sold inone geographic market to have different features than those sold inother geographic markets). In this situation, information coded onto thetest strip may be used by the test meter to determine that the teststrip did not originate in the designated geographic market andtherefore may not provide the features required by regulation, in whichcase the test may be aborted or flagged.

Further, a business model (subscription business model) may be appliedfor the distribution of test strips where proliferation of the teststrips into other sales channels is not desired. For example, users mayenroll into a subscription program in which they are provided with atest meter designed for use by subscription participants, and thesubscription participants may be provided with subscription test stripson a regular basis (for example by mail or any other convenient form ofdelivery). Using the techniques of the present invention, the“subscription test strips” may be encoded to indicate that they weresupplied to a subscription participant. For a variety of reasons, themanufacturer of the subscription test strips may not want thesubscription test strips to be sold in other channels of trade. One wayto prevent this is to design test meters provided to users who are notsubscription participants that will not work with subscription teststrips. Therefore, the present invention may be used to provide testmeters to subscription participants in the subscription business modelthat are programmed to accept subscription test strips encoded toindicate that they are delivered to a user on the basis of asubscription, while other test meters are programmed not to acceptsubscription test strips so encoded.

As a further example, the test meter can have certain functionalities(software- and/or hardware-implemented) designed into the meter that arenot active when the test meter is first sold. The performance of thetest meter can then be upgraded at a later date by including informationencoded on the test strips sold at that later time that will berecognized by the meter as an instruction to activate these latentfeatures. As used herein, the phrase “activating a latent feature of thetest meter” comprehends turning on a test meter functionality thatpreviously was not active, such that the test meter functionalitythereafter remains activated indefinitely (i.e. after the current testwith the present test strip is finished).

Another example of information that can be encoded onto the test stripusing the present invention is an indication of whether the test stripwas sold to the hospital market or to the consumer market. Having thisinformation may allow the test meter to take action accordingly, such asdisplaying user instructions in less detail for the hospitalprofessional. It will be appreciated by those skilled in the art that avariety of types of communication between the test strip and the testmeter may be facilitated by the information encoding provided by thepresent invention.

A second embodiment test strip configuration that allows information tobe encoded directly onto the test strip is illustrated in FIG. 10 andindicated generally at 300. The test strip 300 may preferably be formedgenerally as described above with respect to the test strips 10 and 401,with working 320, counter 322, dose sufficiency working 324, and dosesufficiency counter 326 electrodes may be formed as shown and coupled,respectively, to measurement contact pads W, C, DW and DC. These contactpads provide a conductive area upon the test strip 300 to be contactedby an electrical connector contact of the test meter once the test strip300 is inserted into the test meter. The test strip may be formed with asample inlet in the distal end of the test strip (as shown in FIG. 10),or with a sample inlet on the side of the test strip as shown in FIG. 1.The functionality of the information encoding portion thereof is notaffected by the positioning of the measurement electrodes in eitherposition.

It will be noted from an examination of FIG. 10 that the areasurrounding the counter electrode contact pad C is formed to provide arelatively large expanse of conductive layer, which is divided intoinformation contact pad positions B1-B7. In the second embodiment of thepresent invention, the conductive layer may be formed during manufactureof the test strip such that the conductive layer is either present orabsent within each of the contact pad positions B1-B7, depending uponwhat number is to be encoded onto the test strip 300. It should be notedthat the counter electrode contact pad C is always formed with theconductive layer present in this area, as this contact pad is alwaysnecessary for the making of measurements.

Each of the contact pads C, W, DC and DW, as well as each of the contactpad positions B1-B7 are contacted by individual contacts of a multi-pinelectrical connector located within the test meter when the test strip300 is inserted into the test meter. The multi-pin electrical connectorallows electrical signals to be applied from the test meter to the teststrip and vice versa. The test meter is programmed (by means well-knownin the art), to measure the conductivity between the counter electrodecontact pad C and each of the contact pad positions B1-B7. The contactpad C can therefore be selectively conductively coupled to each of thecontact pad positions B1-B7 depending upon whether the conductive layeris formed, respectively, in each of the contact pad positions B1-B7. Bymeasuring the conductivity between the contact pad C and each of thecontact pad positions B1-B7, the test meter is able to determine thepresence or absence of the conductive layer in each of the contact padpositions B1-B7. By assigning, for example, a digital value of “1” whenthe conductive layer is present in a particular contact pad position anda digital value of “0” when the conductive layer is absent in aparticular contact pad position, a digital word may be encoded onto thetest strip 300.

It will be appreciated that all of the desirable benefits discussedhereinabove with respect to the first embodiment of the presentinvention may also be achieved using the second embodiment of thepresent invention. The second embodiment has the added advantage that,because the contact pad positions B1-B7 can never be conductivelycoupled to more than one measurement electrode, there are no “forbidden”states and each of the contact pad positions B1-B7 may be coded as a “0”or “1” in any possible seven digit digital word to be encoded onto thetest strip. This provides 2⁷ or 128 possible unique words that can beencoded onto the test strip using the contact pad positions B1-B7. Thenumber of contact pad positions that can be designated for suchinformation encoding is only limited by the available space on the teststrip surface, the resolution of the process used to define theconductive features on the test strip, the electrical connector contactspacing, and the tolerance stack-ups relevant to placing the connectorcontact on the contact pad position once the test strip is inserted intothe test meter.

Furthermore, the number of possible states in the second embodiment ofthe present invention can be further increased by severing theconductive path between individual pairs of the contact pad positionsB1-B7. Therefore, a connector contacting contact pad B1 (for example)can check for electrical continuity not only with contact pad C (asdescribed hereinabove), but also for electrical continuity with any ofthe other contact pads B2-B7.

The laser ablation process described hereinabove allows for resolutionof test strip conductive features not previously achievable using priorart techniques such as screen printing and photolithography. Because ofthis, relatively large quantities of data can be coded onto the teststrip when the conductive features are formed using the laser ablationprocess. For example, a third embodiment of the present invention isillustrated in FIG. 11 and indicated generally at 500. The test strip500 is similar to the test strip 300 of FIG. 10, except that theresolution of the laser ablation process allows for an even greaternumber of contact pads to be formed on the test strip. Equivalentstructures in FIG. 11 are given the same reference designators as usedin FIG. 10. A total of sixteen contact pads are formed on the test strip500, with B1-B10 being designated as information contact pads inaddition to the measurement contact pads W, WS, C, CS, DW and DC coupledto working 520, counter 522, dose sufficiency working 524, and dosesufficiency counter 526 electrodes. These contact pads provide aconductive area upon the test strip 500 to be contacted by an electricalconnector contact of the test meter once the test strip 500 is insertedinto the test meter. The test strip may be formed with a sample inlet inthe distal end of the test strip (as shown in FIG. 11), or with a sampleinlet on the side of the test strip as shown in FIG. 1. Thefunctionality of the information encoding portion thereof is notaffected by the positioning of the measurement electrodes in eitherposition.

As with the second embodiment of FIG. 10, it will be noted from anexamination of FIG. 11 that the area surrounding the counter electrodecontact pad C is formed to provide a relatively large expanse ofconductive layer, which is divided into information contact padpositions B1-B10. In the third embodiment of the present invention, theconductive layer may be formed during manufacture of the test strip suchthat the conductive layer is either present or absent within each of thecontact pad positions B1-B10, depending upon what number is to beencoded onto the test strip 500. As noted hereinabove, the counterelectrode contact pad C is always formed with the conductive layerpresent in this area, as this contact pad is always necessary for themaking of measurements.

Each of the contact pads C, CS, W, WS, DC and DW, as well as each of thecontact pad positions B1-B10 are contacted by individual contacts of amulti-pin electrical connector located within the test meter when thetest strip 500 is inserted into the test meter. The multi-pin electricalconnector allows electrical signals to be applied from the test meter tothe test strip and vice versa. The test meter is programmed to measurethe conductivity between the counter electrode contact pad C and each ofthe contact pad positions B1-B10. The contact pad C can therefore beselectively conductively coupled to each of the contact pad positionsB1-B10 depending upon whether the conductive layer is formed,respectively, in each of the contact pad positions B1-B10. By measuringthe conductivity between the contact pad C and each of the contact padpositions B1-B10, the test meter is able to determine the presence orabsence of the conductive layer in each of the contact pad positionsB1-B10. By assigning, for example, a digital value of “1” when theconductive layer is present in a particular contact pad position and adigital value of “0” when the conductive layer is absent in a particularcontact pad position, a digital word may be encoded onto the test strip500.

It will be appreciated that, as with the second embodiment, all of thedesirable benefits discussed hereinabove with respect to the firstembodiment of the present invention may also be achieved using the thirdembodiment of the present invention. Like the second embodiment, thethird embodiment has the added advantage that, because the contact padpositions B1-B10 can never be conductively coupled to more than onemeasurement electrode, there are no “forbidden” states and each of thecontact pad positions B-B10 may be coded as a “0” or “1” in any possibleten digit digital word to be encoded onto the test strip. This provides2¹⁰ or 1,024 possible unique words that can be encoded onto the teststrip using the contact pad positions B1-B10.

Furthermore, as with the second embodiment test strip 300, the number ofpossible states in the third embodiment test strip 500 of the presentinvention can be further increased by severing the conductive pathbetween individual pairs of the contact pad positions B1-B10. Therefore,a connector contacting contact pad B1 (for example) can check forelectrical continuity not only with contact pad C (as describedhereinabove), but also for electrical continuity with any of the othercontact pads B2-B10. This greatly increases the number of unique digitalwords that can be encoded onto the test strip 500.

It should be noted that the contact pad densities achieved in thepresent invention through the use of the laser ablation processrepresent a significant advancement over the prior art. For example,published European patent application EP 1 024 358 A1 discloses a systemwhich uses up to 35 contact pads on a single test strip; however, thedensity of features is so low that the inventors are forced to contactonly five of those contact pads at any one time. Not only does thisrequire much more test strip surface area than the present invention toform the same number of contact pads, but it is impossible for the testmeter to make conductivity checks between each of the contact padsbecause the test meter is never in contact with more than five of thecontact pads at any one time. The tight control of feature dimensionsenabled by the laser ablation process of the present invention allowsfor the use of contact pad density never before achieved in the art. Forexample, the embodiment of FIG. 10 allows eleven contact pads to becontacted simultaneously by the test meter connector. Even greaterdensity is achieved in the embodiment of FIG. 11, where sixteen contactpads may be contacted simultaneously by the test meter connector. Someembodiments of the present invention therefore preferably include atleast ten test strip contact pads coupled to at least ten test meterconnector contacts; more preferably include at least eleven test stripcontact pads coupled to at least eleven test meter connector contacts;and most preferably includes at least fifteen test strip contact padscoupled to at least fifteen test meter connector contacts.

FIGS. 12-14 illustrate a preferred embodiment multiple-pin electricalconnector mating with the third embodiment test strip 500 of FIG. 11.The electrical connector is housed in the test meter (not shown) andincludes multiple contacts that produce contact traces 502 when matedwith respective contact pads on the test strip 500 when the test strip500 is inserted into the test meter electrical connector. FIG. 13illustrates the nominal case in which each electrical connector contactis positioned approximately at the center of the respective test strip500 contact pad when the test strip 500 is mated to the test meter. Inthe preferred embodiment, the tolerances of the placement of theconductive features on the test strip 500, as well as the tolerances ofthe placement of the electrical connector contacts with respect to thetest strip mating port of the test meter are controlled such that theworst case tolerance stack-ups will still result in reliable contactbetween each connector contact and the respective contact pad. As can beseen in FIG. 12, when all of the tolerances are at their maximum so asto move the connector contacts left with respect to their respectivecontact pads, the electrical contacts are still positioned to makereliable electrical contact with the respective contact pad, and all ofthe contact pads B1-B10 are still electrically connected to the contactpad C (if their respective metallization is present) even if themechanical interaction of the connector contacts with the test stripduring insertion completely removes the metallization in the areas ofcontact traces 502. Similarly, as can be seen in FIG. 14, when all ofthe tolerances are at their maximum so as to move the connector contactsright with respect to their respective contact pads, the electricalcontacts are still positioned to make reliable electrical contact withthe respective contact pad, and all of the contact pads B1-B10 are stillelectrically connected to the contact pad C (if their respectivemetallization is present) even if the mechanical interaction of theconnector contacts with the test strip during insertion completelyremoves the metallization in the areas of contact traces 502.

A fourth embodiment test strip of the present invention is schematicallyillustrated in FIG. 15 and designated as 600. The test strip 600 issimilar to the test strip 300 of FIG. 10, except that the fourthembodiment uses only six contact pads on the test strip. Embodimentsusing fewer or more contact pads are contemplated by the presentinvention. Equivalent structures in FIG. 15 are given the same referencedesignators as used in FIG. 10. The test strip includes a workingelectrode 320, a counter electrode 322, a dose sufficiency workingelectrode 324, and two potential dose sufficiency counter electrodes326A and 326B. Each of the electrodes is coupled to at least one contactpad formed on the test strip 600.

The working electrode 320 is coupled to both a W and a WS contact pad.The counter electrode 322 is coupled to a C contact pad and a CS contactpad, although which contact pad is designated as C is optional asexplained hereinbelow. The dose sufficiency working electrode 324 iscoupled to a DW contact pad. The dose sufficiency counter electrode326A/326B is coupled to a DC contact pad, although which contact pad isdesignated as DC is optional as explained hereinbelow.

The test strip 600 allows a single binary bit to be encoded onto thetest strip 600, depending on which of the two potential conductive links602 and 604 are formed on the test strip 600. At least one of thepotential conductive links 602/604 is preferably formed on the teststrip 600, and both potential conductive links 602/604 may not be formedat the same time without losing the second separate dose sufficiencyelectrode functionality.

If the potential conductive link 602 is formed on the test strip 600 andthe potential conductive link 604 is not formed, then the contact pad606 becomes the C contact pad (since it is coupled to the counterelectrode 322 by the potential conductive link 602). Without thepresence of the potential conductive link 604, electrode 326B functionsas the actual dose sufficiency counter electrode and contact pad 608becomes the DC contact pad.

Similarly, if the potential conductive link 604 is formed on the teststrip 600 and the potential conductive link 602 is not formed, then thecontact pad 608 becomes the C contact pad (since it is coupled to thecounter electrode 322 by the potential conductive link 604). Without thepresence of the potential conductive link 602, electrode 326A functionsas the actual dose sufficiency counter electrode and contact pad 606becomes the DC contact pad.

Once the test strip 600 is inserted into the test meter, the test metercan easily determine if the potential conductive link 602 is present bychecking the conductivity between the CS contact pad and the contact pad606. Conductivity between these two contact pads indicates the presenceof the potential conductive link 602. Similarly, the test meter candetermine if the potential conductive link 604 is present by checkingthe conductivity between the CS contact pad and the contact pad 608.Conductivity between these two contact pads indicates the presence ofthe potential conductive link 604. Once the test meter has determinedwhich potential conductive link 602/604 is present, it thereafter knowswhich contact pad to treat as the C contact pad and which to treat asthe DC contact pad. In one embodiment, the test meter only checks forthe presence or absence of one of the potential conductive links 602/604and assumes that the other potential conductive link 602/604 is absentor present, respectively. In another embodiment, the test meter confirmsthe presence or absence of both potential conductive links 602/604,which is a more robust methodology as it is more likely to detect adamaged test strip.

In another embodiment, the code key inserted into the test meter tellsthe test meter which of the two possible configurations to expect. Thetest meter then checks to see if the expected contact pad 606/608 iscoupled to the CS contact pad. If the expected connection is notpresent, then the meter checks to see if the other contact pad 606/608is coupled to the CS contact pad. If the wrong contact pad 606/608 iscoupled to the CS contact pad, then the meter indicates a code key error(i.e. a code key has been inserted into the test meter that does notmatch the test strip inserted into the test meter). If neither contactpad 606/608 is coupled to the CS contact pad, then the test meterindicates a strip error (i.e. the test strip is defective and cannot beused).

More importantly than assigning contact pad functionalities, bydetermining which potential conductive link 602/604 is present, the testmeter has been supplied with one bit of information from the test strip600. This single bit of information can convey important information tothe test meter, such as whether the test strip is designed to test for afirst analyte or a second analyte, where the test meter should look forcalibration information relating to the test strip, etc. Therefore,supplying a single bit of information by simply reassigning thefunctions of some of the contact pads on the test strip can easilyprovide important information to the test meter about the test stripthat has been inserted therein.

All publications, prior applications, and other documents cited hereinare hereby incorporated by reference in their entirety as if each hadbeen individually incorporated by reference and fully set forth.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the description is to be consideredas illustrative and not restrictive in character. Only the preferredembodiment, and certain other embodiments deemed helpful in furtherexplaining how to make or use the preferred embodiment, have been shown.All changes and modifications that come within the spirit of theinvention are desired to be protected.

1. A method for reading information on a test strip, the methodcomprising the steps of: providing a test strip configured to receive abiological fluid sample and having a substrate with a top surface, aconductive layer formed on at least a portion of the substrate topsurface and forming at least one electrode conductively coupled to acontact pad, and at least two separate and distinct contact padpositions defined upon the substrate top surface; providing a test meterfor measuring a concentration of an analyte of interest in thebiological fluid sample on the test strip, the test meter having atleast three connector contacts; inserting the test strip into the testmeter such that each one of the at least three connector contactsseparately and distinctly contacts a respective one, and only one, ofthe contact pad and the at least two contact pad positions; after thetest strip is fully inserted into the meter, detecting with the testmeter one or both of (i) the presence or absence of conductivity betweenthe contact pad and each of the at least two contact pad positions, and(ii) the presence or absence of conductivity between each of the atleast two contact pad positions and each of the other contact padpositions; and assigning within the test meter a first binary bit toeach detected presence of conductivity and a second binary bit to eachdetected absence of conductivity; wherein the compilation of binary bitscomprises a plurality of unique words encoded on the test strip.
 2. Themethod of claim 1, wherein the at least two contact pad positionscomprise at least seven contact pad positions and the at least threeconnector contacts comprise at least eight connector contacts.
 3. Themethod of claim 1, wherein the plurality of unique words comprises up to128 unique words.
 4. The method of claim 1, wherein the at least twocontact pad positions comprise at least twelve contact pad positions andthe at least three connector contacts comprise at least thirteenconnector contacts.
 5. The method of claim 1, wherein the plurality ofunique words comprises up to 1,024 unique words.
 6. The method of claim1, wherein the plurality of unique words relate to a lot ID for the teststrip.
 7. The method of claim 1, wherein the plurality of unique wordsrelate to one or more information selected from the group consisting of:lot ID for the test strip, instruction to activate or deactivate atleast one feature programmed into the test meter, geographic marketinformation, selection of display language for the meter, anddesignation of the test strip as part of a subscription business model.8. A system, comprising: a test strip configured to receive a biologicalfluid sample and having a substrate with a top surface, a conductivelayer formed on at least a portion of the substrate top surface andforming at least one electrode conductively coupled to a contact pad,and at least two separate and distinct contact pad positions definedupon the substrate top surface; a test meter configured and adapted tomeasure a concentration of an analyte of interest in the biologicalfluid sample on the test strip, the test meter having at least threeconnector contacts and being configured to receive the test strip suchthat each one of the at least three connector contacts separately anddistinctly contacts a respective one, and only one, of the contact padand the at least two contact pad positions; the test meter beingconfigured and adapted to detect, only after the test strip is fullyinserted into the meter, one or both of (i) the presence or absence ofconductivity between the contact pad and each of the at least twocontact pad positions, and (ii) the presence or absence of conductivitybetween each of the at least two contact pad positions and each of theother contact pad positions; the test meter being further configured andadapted to assign a first binary bit to each detected presence ofconductivity and a second binary bit to each detected absence ofconductivity; wherein the compilation of binary bits assigned by thetest meter comprises a plurality of unique words encoded on the teststrip.
 9. The system of claim 8, wherein the at least two contact padpositions comprise at least seven contact pad positions and the at leastthree connector contacts comprise at least eight connector contacts. 10.The system of claim 8, wherein the plurality of unique words comprisesup to 128 unique words.
 11. The system of claim 8, wherein the at leasttwo contact pad positions comprise at least twelve contact pad positionsand the at least three connector contacts comprise at least thirteenconnector contacts.
 12. The system of claim 8, wherein the plurality ofunique words comprises up to 1,024 unique words.
 13. The system of claim8, wherein the plurality of unique words relate to a lot ID for the teststrip.
 14. The system of claim 8, wherein the plurality of unique wordsrelate to one or more information selected from the group consisting of:lot ID for the test strip, instruction to activate or deactivate atleast one feature programmed into the test meter, geographic marketinformation, selection of display language for the meter, anddesignation of the test strip as part of a subscription business model.15. The method of claim 1 in which said detecting comprises detecting,after the test strip is fully inserted into the meter, (i) the presenceor absence of conductivity between the contact pad and each of the atleast two contact pad positions.
 16. The method of claim 1 in which saiddetecting comprises detecting, after the test strip is fully insertedinto the meter, (ii) the presence or absence of conductivity betweeneach of the at least two contact pad positions and each of the othercontact pad positions.
 17. The method of claim 1 in which said detectingcomprises detecting, after the test strip is fully inserted into themeter, both (i) the presence or absence of conductivity between thecontact pad and each of the at least two contact pad positions, and (ii)the presence or absence of conductivity between each of the at least twocontact pad positions and each of the other contact pad positions. 18.The system of claim 8 in which the test meter is configured and adaptedto detect, only after the test strip is fully inserted into the meter,(i) the presence or absence of conductivity between the contact pad andeach of the at least two contact pad positions.
 19. The system of claim8 in which the test meter is configured and adapted to detect, onlyafter the test strip is fully inserted into the meter, (ii) the presenceor absence of conductivity between each of the at least two contact padpositions and each of the other contact pad positions.
 20. The system ofclaim 8 in which the test meter is configured and adapted to detect,only after the test strip is fully inserted into the meter, both (i) thepresence or absence of conductivity between the contact pad and each ofthe at least two contact pad positions, and (ii) the presence or absenceof conductivity between each of the at least two contact pad positionsand each of the other contact pad positions.